Motor heat - which way do I go with the gearing?

[BrianG]

Originally Posted by VintageMA

Was reading through another thread and think I may have found a reason temps on the motor were up a bit - running 10K in the center diff but with the torque of the 5S setup the front end was pulling up and unloading a lot. I think a lot of my acceleration was lost in front wheel spin - I might try 15K or 20K in the center and see how that does.

That's how I blew a 10XL on my Revo. The CD I used had too-thin oil in it and unloaded the motor too much. Overheated and after a while had really crappy speed AND really hot motor. Took the CD out and replaced the motor with a 9XL and no problems since. I just couldn't find the happy medium for diff oil that would offer better on-power cornering while not unloading the front.

[VintageMA]

Been a little while, but I tested both 15 and 13 gearing on this setup.

At 15 the motor temp was just a few degrees higher, nothing bad. Current draw did go up as well.

Interesting thing though was that at 13 gearing the motor temp shot up to almost 190* after a 10 minute run. This run was also with my new MMM.

I found it very interesting:
The buggy was very smooth on 5S compared with the MM, but my batteries were really hot - measured 140* on one spot on the battery.

I am a little concerned about that as I have never measured any of my batteries to be that hot unless I was running a way out of whack configuration to test things out.

I recall Patrick saying in one of the MMM threads that there was too much energy in the braking to dissapate the heat through the heat sink and thus the MMM was using a regnenerative power braking setup that would push the current back into the battery. This actually concerns me a lot. LiPos aren't designed to be charged at a high current - 1C is best for charging, 2 - 2.5C is possible with a balancer but will decrease battery life cycles by almost 50%. I believe NiMH can handle higher charge currents better. If this is the case, I will be very dissapointed if my battery life is decreased because of the braking method employed.

How much current do you think the braking could push back into the battery? 2C, 3C, 5C, 10C....... more?